<html> 
<head> 
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> 
<script type="text/javascript"> 
var isIE = /msie/i.test(navigator.userAgent) && !window.opera; 
function fileChange(target,id) { 
	var fileSize = 0; 
	var filetypes =[".jpg",".png",".rar",".txt",".zip",".doc",".ppt",".xls",".pdf",".docx",".xlsx"]; 
	var filepath = target.value; 
	var filemaxsize = 1024*2;//2M 
	if(filepath){ 
		var isnext = false; 
		var fileend = filepath.substring(filepath.indexOf(".")); 
		if(filetypes && filetypes.length>0){ 
			for(var i =0; i<filetypes.length;i++){ 
				if(filetypes[i]==fileend){ 
					isnext = true; 
					break; 
				} 
			} 
		} 
		if(!isnext){ 
		alert("不接受此文件类型！"); 
		target.value =""; 
		return false; 
		} 
	}else{ 
		return false; 
	} 
	if (isIE && !target.files) { 
		var filePath = target.value; 
		var fileSystem = new ActiveXObject("Scripting.FileSystemObject"); 
		if(!fileSystem.FileExists(filePath)){ 
			alert("附件不存在，请重新输入！"); 
			return false; 
		} 
		var file = fileSystem.GetFile (filePath); 
		fileSize = file.Size; 
	} else { 
		fileSize = target.files[0].size; 
	} 

	var size = fileSize / 1024; 
	if(size>filemaxsize){ 
		alert("附件大小不能大于"+filemaxsize/1024+"M！"); 
		target.value =""; 
		return false; 
	} 
	if(size<=0){ 
		alert("附件大小不能为0M！"); 
		target.value =""; 
		return false; 
	} 
} 
</script> 
</head> 
<body> 
<input type="file" name="contractFileName" style="width: 500px;" onchange="fileChange(this);"/> 
</body> 
</html> 